On Mar 5 21:12, Robert Wruck wrote: > Hi, > > recently, I found that cygwin-git was not able to 'cat-file' files > that exceeded some size (in my case about 80MB). > I tracked this down to the cygwin implementation of write() that > behaves quite odd in some cases. > > I wrote a small program (source attached) that mmaps a given file > and tries to write it to another file or stdout. > > The results vary: > > If the destination is a file (`writetest infile outfile` or > `writetest infile > outfile`), the write succeeds in a single call. > > If the destination is a pipe (`writetest infile | cat > outfile`), > the write succeeds in most cases. BUT: > > Under WinXP (XP Service Pack 2, 32bit), the call returns -1 and > errno=EAGAIN. Nevertheless, SOME data is written to the pipe (in my > case 4096 byte for each call). > This breaks git since it does an infinite loop while errno=EAGAIN.
Hang on, you are saying that a *blocking* write(2) to a pipe returns with EAGAIN? Are you sure? It would be quite a surprise if git would actually do that. EAGAIN is only an expected error for non-blocking I/O, so applications which use blocking I/O usually only test for EINTR. Where you able to reproduce the issue with the testcase you attached to your mail? If so, you forgot to add a hint how to use it and an example of the expected outcome. That would be quite helpful. > Any ideas where to investigate further? EAGAIN is set for example in > fhandler.cc, fhandler_base_overlapped::has_ongoing_io but I don't > know whether that function is involved in my case. It is. The overlapped io stuff is only used for pipes and fifos right now. Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Project Co-Leader cygwin AT cygwin DOT com Red Hat -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple
